Tube cell for atomic absorption spectrophotometry

Abstract

A tube cell for flameless atomic absorption spectrophotometry has a transverse cross-section with the portion above a longitudinally extending line midway between the top and bottom of the tube cell having a smaller cross-sectional area than the portion below that line. The tube cell has an elongated aperture formed close to the bottom of the tube cell for inserting a probe or platform carrying a sample to be analyzed. The cross-section of the tube cell is shaped to maximize the size of the probe which can be used, and accordingly, the sample volume, while keeping the total cross-sectional area to a minimum in order to maximize chemical sensitivity. A number of different cross-sectional shapes are described including a triangular cross-section.

What is claimed is: 
     
       1. A tube cell for an atomic absorption spectrophotometer comprising a tubular body of electrically conductive material having a length with a longitudinal axis extending substantially horizontal,   said tubular body having a cross-section in a plane transverse to said longitudinal axis, said transverse cross-section being at least a minimum at the center of said length of said tubular body, and   said tubular body having a cross-sectional area for said transverse cross-section above a horizontal line midway between a top and a bottom of said tubular body, said cross-sectional area above said horizontal line being smaller than the cross-sectional area for said transverse cross-section of said tubular body below said horizontal line.   
     
     
       2. A tube cell according to claim 1, wherein said transverse cross-section increases in area from said center toward ends of said tubular body. 
     
     
       3. A tube cell according to claim 1, wherein said transverse cross-section is substantially constant in area along said length of said tubular body. 
     
     
       4. A tube cell according to claim 1, wherein a dosing aperture is formed in an upper surface at said center of said tubular body. 
     
     
       5. A tube cell according to claim 4, wherein an elongated aperture is formed toward said bottom of said tubular body, said elongated aperture being at said center of said tubular body. 
     
     
       6. A tube cell according to claim 4, wherein said transverse cross-section is trapezoidal with parallel sides extending horizontally. 
     
     
       7. A tube cell according to claim 4, wherein said transverse cross-section is triangular with one side of the triangle being substantially horizontal. 
     
     
       8. A tube cell according to claim 4, wherein said tubular body is flared from said center toward both ends. 
     
     
       9. A tube cell according to claim 4, wherein said tubular body is formed totally of pyrolytic graphite by chemical vapor deposition on a mandrel. 
     
     
       10. A tube cell according to claim 1 or claim 2 or claim 3, wherein an elongated aperture is formed toward said bottom of said tubular body, said elongated aperture being at said center of said tubular body. 
     
     
       11. A tube cell according to claim 1 or cliam 2 or claim 3, wherein said transverse cross-section is trapezoidal with parallel sides extending horizontally. 
     
     
       12. A tube cell according to claim 1 or claim 2 or claim 3, wherein said transverse cross-section is triangular with one side of the triangle being substantially horizontal. 
     
     
       13. A tube cell according to claim 1 or claim 2 or claim 3, wherein said tubular body is formed totally of pyrolytic graphite by chemical vapor deposition on a mandrel. 
     
     
       14. A tube cell according to claim 1, wherein a pocket extends below said tubualr member, said pocket communicating with the interior of said tubular body, and said pocket being formed midway between ends of said tubular body, and wherein an elongated aperture is provided in said pocket. 
     
     
       15. A tube cell according to claim 14, wherein a dosing aperture is formed in an upper surface at said center of said tubular body. 
     
     
       16. A tube cell according to claim 15, wherein said transverse cross-section is trapezoidal with parallel sides extending horizontally. 
     
     
       17. A tube cell according to claim 15, wherein said transverse cross-section is triangular with one side of the triangle being substantially horizontal. 
     
     
       18. A tube cell according to claim 15, wherein said tubular body is flared from said center toward both ends. 
     
     
       19. A tube cell according to claim 3, wherein a dosing aperture is formed in an upper surface at said center of said tubular body. 
     
     
       20. A tube cell according to claim 19, wherein an elongated aperture is formed towards said bottom of said tubular body, said elongated aperture being at said center of said tubular body. 
     
     
       21. A tube cell according to claim 19, wherein said transverse cross-section is trapezoidal with parallel sides extending horizontally. 
     
     
       22. A tube cell according to claim 19, wherein said transverse cross-section is triangular with one side of the triangle being substantially horizontal. 
     
     
       23. A tube cell according to claim 19, wherein said tubular body is formed totally of pyrolitic graphite by chemical vapor deposition on a mandrel. 
     
     
       24. A tube cell according to claim 3, wherein a pocket extends below said tubular member, said pocket communicating with the interior of said tubular body, and said pocket being formed midway between ends of said tubular body, and wherein an elongated aperture is provided in said pocket. 
     
     
       25. A tube cell according to claim 24, wherein a dosing aperture is formed in an upper surface at said center of said tubular body. 
     
     
       26. A tube cell according to claim 25, wherein said transverse cross-section is trapezoidal with parallel sides extending horizontally. 
     
     
       27. A tube cell according to claim 25, wherein said transverse cross-section is triangular with one side of the triangle being substantially horizontal. 
     
     
       28. A tube cell for an atomic absorption spectrophotometer comprising a tubular body of electrically conductive material having a length with a longitudinal axis being substantially horizontal,   a pocket extending below said tubular body, said pocket communicating with the interior of said tubular body, and said pocket being formed midway between ends of said tubular body, and   an elongated aperture in said pocket.